Button appears twice at reRenders through a4j

[Vadim Vararu]

I've got this portion to reRender and i don't understand why after reRender the button appears twice on the page:

    
<h:panelGroup id="quitterContainer">
<h:form>
<button onclick="Richfaces.showModalPanel('confirmQuitterPanel')" id="bouttonQuitterProduitId" class="button" type="button">
<div class="buttonText">Quitter</div>
</button>
<h:outputText value="#{preparationInventaireBean.composite}" />
</h:form>
</h:panelGroup>